The present application claims priority under 35 U.S.C. xc2xa7119 to Japanese Patent Application No. 11-274337 filed on Sep. 28, 1999 and Japanese Patent Application No. 2000-242180 filed on Aug. 10, 2000. The contents of these applications are incorporated herein by reference in their entirety.
1. Field of the Invention
The present invention relates to an intermediate transfer belt for an image forming apparatus employing an electrophotographic method such as a photocopier, a printer, a facsimile, and similar image forming apparatus, and more particularly, to a method of producing the intermediate transfer belt for the image forming apparatus.
2. Discussion of the Background
In a known image forming apparatus employing an electrophotographic method, to form a toner image on a transfer material, first, an electrostatic latent image is formed on a surface of a photoreceptor including photoconductive element serving as a first image bearing member by a latent image forming device including a charging device, an exposing device, etc. Subsequently, the electrostatic latent image on the photoreceptor is developed with toner by a developing device, and then the toner image is transferred to the transfer material serving as a second image bearing member by a transfer device including a transfer charger, a transfer roller, etc. The transferred toner image is fixed on the transfer material under the influence of heat and pressure by a fusing device including a fusing roller, a pressure roller, etc., and thereby a print image is obtained.
Further, as a full-color image forming method, there are, for example, two types of known image forming methods.
In the first type full-color image forming method, first, a latent image forming device forms an electrostatic latent image corresponding to each color component image obtained by separating an original image into each color component image on a photoreceptor. Each electrostatic latent image is developed with a corresponding color toner such as yellow, magenta, cyan, and black toners which are respectively deposited in developing units. Then, under the condition that a transfer material is held on a transfer material bearing member such as a transfer drum, yellow, magenta, cyan, and black toner images formed on the photoreceptor are transferred onto the transfer material by each color by a transfer device such that respective color toner images are superimposed on each other on the transfer material. Subsequently, the transfer material is separated from the transfer material bearing member. The toner image transferred onto the transfer material is fixed by a fixing device, and thereby a full-color image is obtained.
On the other hand, for example, Japanese Laid-open Patent Publication No. 5-11562 describes a multi-color image forming apparatus employing the second type full-color image forming method wherein respective color toner images developed on a photoreceptor are not directly transferred onto a transfer material. Specifically, color toner images developed on the photoreceptor are transferred onto an intermediate transfer member that rotates in synchronization with the rotations of the photoreceptor by each color by a primary transfer device (transfer from the photoreceptor to the intermediate transfer member may be hereinafter referred to as a primary transfer). The transferred color toner images are superimposed on each other on the intermediate transfer member. Subsequently, the toner image is collectively transferred onto the transfer material which is conveyed in synchronization with the rotations of the intermediate transfer member by a secondary transfer device (transfer from the intermediate transfer member to the transfer material may be hereinafter referred to as a secondary transfer). The toner image transferred onto the transfer material is fixed by a fixing device, and thereby a full-color image is obtained.
In an image forming apparatus employing the above-described second type full-color image forming method wherein the intermediate transfer member is used, there is no need for any control on the transfer material, such as, for example, attaching the transfer material onto the surface of the transfer material bearing member, curving the transfer material along the surface of the transfer material bearing member, etc., as compared with the above-described first type full-color image forming method. Therefore, in the image forming apparatus employing the second type full-color image forming method, various kinds of transfer materials can be used regardless of thickness, width, length, etc., such as from a thin paper of about 40 g/m2 to a thick paper of about 200 g/m2, a post card, an envelope, etc. Thus, the second type full-color image forming method has an advantage in versatility in transfer materials.
Although the image forming apparatus using the intermediate transfer member has the above-described advantage in versatility in transfer materials, it has the following problems to be solved.
With the increase of operations of color electrophotographic apparatuses such as a color copier, a color laser printer, etc. in the market, there has been increase in users"" demands for high image quality. Generally, as a background intermediate transfer member, intermediate transfer belts made of resin and produced by an extrusion method have been being much employed. However, in the intermediate transfer belt produced by the extrusion method, transfer unevenness typically occurs due to nonuniformity in resistivity of the intermediate transfer belt in the circumferential direction thereof.
It is assumed that the nonuniform resistivity of the intermediate transfer belt in the circumferential direction thereof is caused by the following reason. In the extrusion method, molten resin materials are injected from a plurality of nozzles into a mold of an extrusion molding device. Then, the resin materials injected from the nozzles are extruded by the mold. When the resin materials are extruded by the mold, the difference in pressure received by the resin materials in the circumferential direction thereof may occur. As a result, a dispersive condition of electrically conductive filler such as carbon black, etc. may be changed, and thereby the resistivity in the intermediate transfer belt in the circumferential direction thereof may turn out to be nonuniform.
Thus, in the image forming apparatus using the intermediate transfer belt produced by the extrusion method, the transfer unevenness which may be caused by the nonuniform resistivity in the intermediate transfer belt in the rotational direction thereof typically occurs.
Also, in intermediate transfer belts produced by a dipping method and an injection molding method, resistivity of the intermediate transfer belts become nonuniform due to uneven dispersion of the electrically conductive filler.
In the above-described intermediate transfer belt, in order to prevent deviation of the position of multi-color toner images which are transferred from the photoreceptor onto the intermediate transfer belt, a position detecting mark is provided so as to detect a rotational position of the intermediate transfer belt and to make transfer starting timings of respective color toner images coincide with each other. For example, in the background image forming apparatus, a reflecting tape is affixed onto a rear surface or a front surface of the intermediate transfer belt as the position detecting mark. A light-reflecting type mark sensor detects the reflecting tape.
The position detecting mark is used as a reference when respective color toner images are sequentially transferred onto the intermediate transfer belt and superimposed on each other. If the position detecting mark is affixed onto the intermediate transfer belt without high accuracy, the position of the transferred color toner images is deviated on the intermediate transfer belt. This deteriorates an image quality of the full-color image transferred onto a transfer material.
Further, in the case of the intermediate transfer belt using the above-described reflecting tape as the position detecting mark, the reflecting tape as a position detecting member and equipment for affixing the reflecting tape to the intermediate transfer belt are required. Moreover, troublesome processing works of affixing the reflecting tape to the intermediate transfer belt is required. As a result, the manufacturing cost is inevitably increased.
Furthermore, in the image forming apparatus using the intermediate transfer belt on which the above-described reflecting tape is affixed, when the intermediate transfer belt is repeatedly rotated, the reflecting tape may be separated from the intermediate transfer belt or may curl up. Consequently, the rotational position of the intermediate transfer belt can not be detected accurately, and thereby primary transfer errors may occur. Therefore, an image forming operation can not be performed properly.
Still furthermore, the position of the reflecting tape affixed on the intermediate transfer belts is likely to be nonuniform. Accordingly, errors in detecting the position of the intermediate transfer belt may be caused.
As an alternative method of detecting the position of the intermediate transfer belt without affixing the above-described reflecting tape onto the intermediate transfer belt, a method using a position detecting hole is known. Specifically, as illustrated in FIG. 21, a slit-shaped position detecting hole 123 is provided at somewhat inside from the one edge of an intermediate transfer belt 110. A mark sensor 124 of light-transmission type detects the position detecting hole 123 as a position detecting mark. For example, Japanese Laid-open Patent Publication No. 5-158314 describes a similar method using slit-shaped position detecting holes.
The slit-shaped position detecting hole 123 is usually formed by making holes through the portion near one edge of the intermediate transfer belt 110 after the intermediate transfer belt 110 is formed in a shape of an endless belt. Accordingly, in a boring process for the position detecting hole 123, the position of the position detecting hole 123 is likely to be nonuniform in the intermediate transfer belt 110. Therefore, similarly as in the above-described intermediate transfer belt using the reflecting tape as the position detecting mark, errors in detecting the rotational position of the intermediate transfer belt 110 are likely to occur in the intermediate transfer belt 110 using the position detecting hole 123 as the position detecting mark. Further, after the position detecting hole 123 is formed in the intermediate transfer belt 110 in the boring process, residue as a waste is unfavorably produced.
The above-described errors in detecting the rotational position of the intermediate transfer belt 110 are likely to occur especially when a plurality of position detecting holes 123 are formed in the intermediate transfer belt 110. When a plurality of position detecting holes 123 are formed in the intermediate transfer belt 110 as illustrated in FIG. 21, three detection signals are sequentially output from the mark sensor 124 at a timing corresponding to a pitch P1 and a pitch P2 between respective position detecting holes 123. The rotational position of the intermediate transfer belt 110 is detected based on the detection signals output from the mark sensor 124. Therefore, the degree of accuracy for detecting the rotational position of the intermediate transfer belt 110 depends on the accuracy of the pitches P1 and P2.
In such a situation, regarding the pitches P1 and P2 between the respective position detecting holes 123, it is required to form the position detecting holes 123 such that, for example, the pitches P1 and P2 usually fall within the tolerance of xc2x13 mm.
However, the respective position detecting holes 123 are formed by boring them in order with a predetermined pitch so as to go along in the rotational direction of the intermediate transfer belt 110. Consequently, even though the pitches between the position detecting holes 123 which are located adjacent to each other fall within the above-described tolerance range, those pitches between the position detecting hole 123 bored first and that bored last may inevitably deviate from the above-described tolerance range due to the accumulation of tolerance therebetween.
For this reason, in the intermediate transfer belt 110 wherein the above-described position detecting holes 123 are formed in the boring process, errors in detecting the rotational position of the intermediate transfer belt 110 occur due to the low accuracy of the pitches P1 and P2 between the respective position detecting holes 123. For example, when the position detecting hole 123 bored first and that bored last are formed extraordinary close to each other due to the above-described accumulation of the tolerance, those two position detecting holes 123 are detected such that the two detection signals output from the mark sensor 124 are sometimes superposed on each other.
In this case, it may be impossible to judge which one of the two position detecting holes 123 is detected based on the detection signal output from the mark sensor 124. As a result, the rotational position of the intermediate transfer belt 110 can not be detected precisely.
The present invention has been made in view of the above-discussed and other problems.
According to the present invention, a novel method of producing a high quality intermediate transfer belt allows an intermediate transfer belt whose position can be detected with high accuracy to be produced at a low cost.
Also, according to the present invention, a novel intermediate transfer belt of high quality for an image forming apparatus allows a position of the intermediate transfer belt to be detected precisely so as to form a high quality image.
Still, according to the present invention, a novel image forming apparatus including a high quality intermediate transfer belt allows a position of the intermediate transfer belt to be detected precisely so as to form a high quality image.
These and other objects can be achieved according to the present invention by a novel method of producing an endless intermediate transfer belt having at least one position detecting hole for detecting a rotational position of the endless intermediate transfer belt in an image forming apparatus, including rotating a cylindrical mold having at least one protruding member on an inner peripheral surface thereof, supplying a liquid material onto the inner peripheral surface of the cylindrical mold wherein the liquid material is formed into the endless intermediate transfer belt and the at least one position detecting hole is formed in the endless intermediate transfer belt by the at least one protruding member, and heating the endless intermediate transfer belt so as to harden the endless intermediate transfer belt, and taking out the endless intermediate transfer belt from the cylindrical mold.
Other objects, features, and advantages according to the present invention will become apparent from the following detailed description when read in conjunction with the accompanying drawings.